1. Field of the Invention
The present invention relates to an image fixing device in an electron photographic image forming apparatus such as a copying machine, a facsimile machine, a printer or the like and more particularly, to an image fixing apparatus using an electromagnetic induction heating, an image forming apparatus providing an image fixing device, and a rotor used in the image fixing device having inside thereof an induction coil.
2. Description of the Related Art
In an image forming apparatus such as a copying machine, a facsimile machine, a printer or the like, generally a toner image is formed on a recording material so that the toner image on the recording material is fixed to the recording material with the image fixing device. This image fixing device includes a heating image fixing device having two fixing rollers, and other kinds of image fixing device. The heating image fixing device having the two rollers fixes the toner image on the recording material to the recording material with heating by the heating rollers having two fixing rollers when the recording material passes through a nib part of the two fixing rollers.
For example, as disclosed in Japanese Patent Application Laid-Open No. 48-59458, there is available a heating roller in this kind of image fixing device which is constituted to incorporate in a main body of a hollow-shaped roller comprising a non-magnetic material an electromagnetic induction heating mechanism comprising an iron core as a shaft shaft and an induction coil which is wound on the iron core. When the induction coil is excited with an alternate current, there is available a heating roller wherein a magnetic flux passes through an internal circumferential wall of the main body of the roller which faces the induction coil, and an alternate current is induced along the circumferential direction and the main body of the roller is heated. In addition, in the image fixing device, it is necessary to maintain the set temperature of the heating roller to a definite level from the viewpoint of uniforming the fixing accuracy (and uniforming the image quality as a result). For example, Japanese Patent Application Laid-Open No. 51-90043 discloses an art wherein the surface temperature of the heating roller is detected with a temperature sensing device which is pressed and is brought into contact with an arbitrary position of the roller surface, and a power input to the induction coil is controlled with a temperature control means on the basis of the detected value.
Furthermore, Japanese Patent Application Laid-Open No. 53-63032 describes a heating roller comprising a jacket which is formed by combining an internal cylinder and an external cylinder to seal a caliber part of one end between both cylinders, a thermal carrier which is sealed in the jacket, and, means for controlling a temperature of a heating part by heating a heating part comprising both cylinders with an induction coil wound around a core which is disposed around the inside of the internal cylinder and detecting an internal pressure of the jacket having an increasing pressure with a temperature detection means including bellows.
Japanese Patent Application Laid-Open No. 53-50844 discloses an art for quickening a rise of the heating roller and eliminating a lack in the strength of a heating layer by providing a heating roller comprising a winding wound around a core comprising a magnetic body fixed to a shaft, a heat insulating layer comprising an elastic body which is arranged on an external circumference of the winding, and a flexible induction heating layer which covers the heat insulating layer.
The heating roller described in the aforementioned Japanese Patent Application Laid-Open No. 53-50844 has a problem in that the cost of the heating roller is high because the heating roller has a structure in which the whole roller including a core part has an integrated structure, and the cost of the heating roller replacement is high because the heating roller as a whole must be replaced at the time of replacing the heating roller.
The heating roller which is described in Japanese Patent Application Laid-Open No. 6-60957 has a core part and an external circumference part as separate entities. When the external circumference part of the heating roller is deteriorated, only the external circumference part may be replaced so that the roller can be replaced at a low cost. However, a thickness of a part where joule heat is generated is thick, and the heat capacity is large so that there is a problem in that the so-called rise time becomes long for realizing a desired fixing temperature.
In addition, the heating roller described in the aforementioned Japanese Patent Application Laid-Open No. 53-50844 is constituted so that the heat insulation layer is arranged only at each end part of the induction heat layer, and a central part of the heating roller is curved in a convex-shape with the result that paper is fed in a stable manner by allowing force to act in a direction of spreading the paper at the time of paper feeding.
Japanese Patent Application Laid-Open No. 2-12791 describes an induction heat roller having a jacket chamber provided on a circumferential surface of a roller which is rotatably supported, the jacket chamber having a two phase thermal carrier in a gas and a liquid state uniformly in an axial direction of the roller; a plurality of induction heat mechanism arranged inside of the roller in an axial direction: and a swell and shrinkage mechanism which either swells or shrinks in a radial direction the roller on an internal surface wall in the roller between the plurality of the induction heat mechanism, wherein the induction heat roller is used as a fixing roller of the heating and image fixing device so that a bending amount by a pressure of the nib part is corrected.
The image fixing device described in Japanese Patent Application Laid-Open No. 53-63032 has the following problems.
a. The temperature of the heating roller is detected with a thermistor or the like outside of the heating roller and a rise of the temperature of the heating roller is detected with the temperature fuse so that the response of the temperature detection is not favorable. PA1 b. In addition, in the case where a separation layer is provided on a surface of the heating roller, the separation layer is damaged with a thermistor or the like so that the endurance of the heating roller is deteriorated. PA1 c. Furthermore, a stain is generated on a part where the temperature is detected with the thermistor of the heating roller or the like so that it is necessary to clean the part at the time of the maintenance. PA1 at least one of temperature detection means for detecting temperature of the rotor which has an induction coil inside to control the high frequency current which is allowed to pass through the aforementioned induction coil; or PA1 temperature over-rise preventing detection means for detecting that the temperature of the aforementioned rotor has risen to a predetermined temperature to prevent the temperature of the aforementioned rotor from rising to a high level. PA1 at least temperature detection means for detecting the temperature for controlling a high frequency current which is allowed to pass through the aforementioned induction coil: or PA1 temperature over-rise preventing detection means for detecting that the temperature of the rotor has risen to a predetermined temperature for preventing the temperature of the rotor from rising to an unusually high level. PA1 temperature detection means for detecting the temperature of a rotor having an induction coil inside to control a high frequency current which is allowed to pass through the aforementioned induction coil; and PA1 a correction means for correcting while a high frequency current is output which is allowed to pass through the aforementioned induction coil with respect to the aforementioned temperature detection means; PA1 wherein the magnetic flux which is generated at the time of induction heating does not affect the temperature detection means, and the temperature detection accuracy is improved. PA1 temperature detection means for detecting the temperature of the aforementioned rotor to control a high frequency current which is allowed to pass through the aforementioned induction coil; and PA1 a correction means for correcting while a high frequency current is output which is allowed to pass through the aforementioned induction coil with respect to the aforementioned temperature detection means; PA1 wherein the magnetic flux which is generated at the time of induction heating does not affect the temperature detection means, and the temperature detection accuracy is improved. PA1 temperature over-rise preventing detection means for detecting that the temperature of the aforementioned rotor has attained a predetermined level to prevent the temperature of the rotor having an induction coil inside from rising to an unusually high level; and PA1 a member formed of a magnetic material arranged in the vicinity of the temperature over-rise preventing detection means; PA1 wherein the response of the temperature over-rise preventing means is improved. PA1 temperature detection means for detecting a surface temperature of the rotor having an induction coil inside; PA1 temperature control means for controlling a high frequency current which is allowed to pass through the aforementioned coil on the basis of a detection value of the aforementioned temperature detection means; PA1 wherein the aforementioned temperature detection means is arranged in correspondence to a position outside of the scope of the aforementioned coil in the axial direction of the aforementioned rotor, and the temperature detection means is alienated as much as possible from the influence scope of the electromagnetic induction heating mechanism to reduce the influence as much as possible thereby accurately detecting the temperature. PA1 temperature detection means for detecting a surface temperature off the rotor; and PA1 temperature control means for controlling a high frequency current which is allowed to pass through the aforementioned induction coil on the basis of the detection value of the aforementioned detection means; PA1 wherein the temperature detection means is arranged in correspondence to a position outside of the scope of the aforementioned induction coil in an axial direction of the aforementioned rotor, the temperature detection means is alienated as much as possible from the influence scope of the electromagnetic induction heating mechanism to minimize the influence so that the temperature can be detected accurately. PA1 temperature detection means for detecting a surface temperature of the rotor having the aforementioned induction coil inside; and PA1 temperature control means for controlling a high frequency current which is allowed to pass through the aforementioned induction coil on the basis of the detection value of the aforementioned temperature detection means; PA1 wherein the aforementioned temperature detection means is covered with a magnetic shield material except for the detection part with respect to the aforementioned rotor, and the periphery of the temperature detection means is shielded from the magnetic field to minimize the influence of the electromagnetic induction heating mechanism thereby accurately detecting the temperature. PA1 temperature detection means for detecting a surface temperature of the aforementioned rotor; and PA1 temperature control means for controlling a high frequency current which is allowed to pass through the aforementioned induction coil on the basis of the detection value of aforementioned temperature detection means; PA1 wherein the aforementioned temperature detection means is covered with a magnetic shield material except for the detection part with respect to the aforementioned rotor, and the periphery of the temperature detection means is shielded from the magnetic field to minimize the influence of the electromagnetic induction heating mechanism thereby accurately detecting the temperature. PA1 temperature detection means for detecting a surface temperature of the rotor having the aforementioned induction coil therein; and PA1 temperature control means for controlling a high frequency current which is allowed to pass through the induction coil on the basis of the detection value of the aforementioned temperature detection means; PA1 wherein the electromagnetic induction heating mechanism including the aforementioned coil is deflected from the shaft of the aforementioned rotor and is alienated from the aforementioned detection means, and the temperature detection means is alienated from the influence scope of the electromagnetic induction heating mechanism to minimize the influence thereby accurately detecting the temperature. PA1 a rotor having an induction coil therein, the rotor comprising three layers, a non-magnetic heat resisting support layer, a thin magnetic heating layer and a separation layer, the three layers being constituted integrally, the three layers being detachable from a flange supporting the aforementioned three layers from both ends thereof, the rotor having a good efficiency and being suitable to a heat roller pair so as to be easily replaceable. PA1 a rotor having an induction coil inside; PA1 a non-conductive cylindrical member formed of the aforementioned the heat resisting non-magnetic material; PA1 a core part which is arranged inside of the aforementioned cylindrical member to generate an induction magnetic flux; PA1 a magnetic and thin hollow cylinder which is loosely fit onto an external circumference of the aforementioned cylindrical member; PA1 engaging means for engaging the aforementioned hollow cylinder to the aforementioned cylindrical member to allow the aforementioned cylinder to integrally rotate with the aforementioned cylindrical member. PA1 a rotor having an induction coil therein; PA1 wherein the support part of the aforementioned shaft is formed of a non-magnetic body; and PA1 a rotor having an induction coil therein wherein a uniform state of the temperature distribution in the axial direction can be obtained, the rotor being capable of being produced favorably in large amounts. PA1 a core formed of a magnetic body fixed to a shaft for supporting the aforementioned rotor, the core having a coil wound thereon; PA1 wherein the support part of the aforemetioned shaft is formed of a non-magnetic body and the uniformity of temperature in the axial direction can be obtained and the mass production thereof is favorable. PA1 an substrate layer and an external layer; PA1 wherein the aforementioned external layer has a magnetic property, and the rise property of the surface temperature can be improved even when a material having a low thermal conduction property is low. PA1 a substrate layer, an intermediate layer and a separation layer; PA1 wherein the aforementioned intermediate layer has a magnetic property and the separation property is not lowered even when the heat conduction of rubber or the like is improved. PA1 a substrate layer, an intermediate layer and a separation layer; PA1 wherein the aforementioned separation layer has a magnetic property and the rise property of the surface temperature can be improved. PA1 said rotor having an induction coil inside which rotor is the rotor; PA1 wherein the rise property of the surface temperature can be improved and the separation property is not lowered. PA1 a substrate layer formed of a non-conductive heat resisting rigid material, a heat resisting elastic layer provided on an external circumference part of the aforementioned substrate, and a separation layer which are formed in this order; PA1 a heating part formed by densely winding a thin linear magnetic body in a spiral configuration; PA1 wherein a winding diameter of the aforementioned linear increases in a direction proceeding from the longitudinal central part of the aforementioned substrate layer to both end parts and the aforementioned linear magnetic body is located nearer to the aforementioned substrate layer at the aforementioned end parts thereof. PA1 the rotor having an induction coil inside being the rotor; PA1 the other rotor being a rotor providing an elastic body with a magnetic property; PA1 wherein a temperature gradient between the rotors can be reduced. PA1 the rotor having the induction coil having an induction heating mechanism including the aforementioned induction coil; PA1 wherein the aforementioned heating mechanism comprises at least two or more independent heating mechanism which is arranged in an axial direction and allows electricity to pass independently and the recording material feeding stability is improved. PA1 an induction heating mechanism including the aforementioned induction coil; PA1 wherein the aforementioned induction heating mechanism comprises at least two independent induction heating mechanism which is arranged in an axial direction of the aforementioned rotor and allows electricity to pass independently and the recording material feeding stability is improved. PA1 a rotor having an induction coil inside, the rotor being capable of most suitably swelling to improve the recording material feeding stability and save energy. PA1 a rotor having an induction coil inside, the rotor swelling to the most appropriate amount suitable to the condition of the recording material to improve the recording material feeding stability and save energy. PA1 manuscript blank part detection means for detecting a blank part of the aforementioned manuscript; PA1 means for turning on and off the passage of electricity of the aforementioned two or more independent induction heating mechanism corresponding to the blank part of the manuscript detected by the aforementioned manuscript blank part detection means; PA1 wherein a rotor having an induction coil swells depending on a part on the recording material where a toner image exists so that energy can be saved. PA1 wherein a surface temperature of the rotor having an induction coil can be controlled independently for each part which is induced and heated with each induction heating mechanism. PA1 wherein a safety mechanism can be functioned with the temperature fuse when any of the two or more independent induction heating mechanism runs away.
Therefore, it is thought to provide a temperature fuse or a thermistor on a paper unfeeding part (where paper does not pass through) of the heating roller to improve the aforementioned disadvantages b and c. In such a case, the temperature at a central part of the heating roller cannot be accurately detected. In addition, in the case where the heating roller is heated with a radiation heat from the outside of the heating roller by means of a halogen heater, the inside of the heating roller becomes high so that there arises a problem in that some device which is to be provided inside of the heating roller suffers from a problem in the heat insulation properties.
In addition, the internal pressure of the jacket is detected with the temperature detecting device including bellows so that the temperature of the heating part is controlled. Consequently, the temperature detection accuracy is not favorable and the device becomes very large. Furthermore, the heating part is heated with the induction coil so that a detection error of the temperature detection means is likely to be generated under an influence of the magnetic flux of induction heating from the induction coil in the case where the temperature detection means used in the device comprises a device formed of a conductive material such as a thermistor or the like.